Electron tube thermoelectric generator



Aug. 14, 1956 w. CALDWELL 2,759,112

ELECTRON TUBE THERMOELECTRIC GENERATOR Filed Aug. 24, 1953 'III";. E

, HIGH VACUUM J ELECTRO'SgAirggSII/E nuv'n S U B 3/ 'A t I E- v/I. 'IIII- ELECTRON EM/S.Y/VE Jl/HSDM/CE INVENTOR i; acids aw, I J H /7 ATTORNEY ELECTRON TUBE THERMOELECTRI'C GENERATGR Winston Caldwell, Nashville, Tenn.

Application August 24, 1953, Serial No. 375,881

Claims. (Cl. 3104) My invention relates to an electron tube designed to convert heat directly into electricity, and particularly to a simple apparatus of this nature which is adapted to and can be used to generate and create a high voltage on commercially useful electric current.

An object of my invention is to provide a device of this character which is simple in construction and operation and which will act efliciently and economically to produce useable power.

Another object is to provide apparatus of this character which is relatively simple and inexpensive in its construction and installation; and which can be installed and used for a variety of uses and power requirements or purposes; and which when placed in use will operate efliciently and inexpensively substantially continuously or as desired, without interruption or requirement for repairs or services.

A further object is the provision of apparatus of this character to utilize large sources of what would otherwise be waste heat, such as heat obtained from solar energy, or from the flue gases of power plants, atomic installations or blast furnaces, or from the exhaust of jet engines and rocket missiles. In the case of waste heat from jet engines and rocket missiles, such apparatus can be used to operate the electrical equipment of the device.

With the above and other objects in view, some of which will be apparent to those skilled in the art and others of which are inherent in the construction and use of the parts, my invention relates to certain novel features of construction and combination and arrangement of parts which will be hereinafter described in connection with the drawings and then pointed out in the claims.

In the drawings:

Figure l is a view somewhat in schematic section showing one embodiment of my invention.

Fig. 2 is a transverse sectional view taken through the showing of Figure 1.

Fig. 3 is a view somewhat similar to Figure 1 showing another embodiment of my invention.

As has been stated, the drawings show two forms or constructions somewhat diagrammatically in which my invention can be embodied.

In the showing in Figures 1 and 2, the cathode structure is made generally cylindrical in form, having a side wall 1 and a central core or flue 2, both of which are connected together and closed at their ends by the top and bottom portions 3 and 4. This construction is made such that the cathode is substantially sealed throughout, and can be evacuated to any degree and extent desired.

A substantially cylindrical or tubular plate 5 is fitted around the wall 1 of the cathode in close proximity thereto, and is insulated from the cathode structure and is sealed by suitable end rings 6 and 7, the space around the cathode and within the plate 5 being thus separated only slightly and being exhausted to a high vacuum.

A commercially useful apparatus would be made with an overall diameter of 5 feet or more, and will be 10 feet to 20 feet tall, with the space between the cathode and the tates Patent Patented Aug. 1 3, 1956 plate quite small, perhaps something like of an inch or less. It is not believed that there is any inherent reason to prevent construction of the device of my invention in any other size that may be practical, except considerations of cost, weight, and other structural considerations. One practical consideration of the successful operation of my device is that the cathode and the plate shall be fairly large and the space between the cathode and the plate shall be quite small.

A burner 8 is disposed at the lower end of the core or flue to direct heat therethrough in such volume as may be necessary to heat the cathode structure to a red heat, or better, or to such heat as may be required for successful operation. This burner 8 can be a gas or oil fed type, and can be of such construction as may be necessary for the particular purpose desired. Fuel can be fed to the burner and can be controlled by various well known means, and no attempt is here made to disclose the some. Further, any type of hood or pipe or other exhaust means can be provided at the upper end of the core or flue 2, as may be necessary under the particular conditions of use.

In the present instance, I have shown the space between the core or flue 2 and the outer wall 1 of the cathode as closely packed or filled with a large number of lengths of fine gauge refractory insulated wire of fine gauge and coated with a refractory insulation or covering suflicient to withstand the heat which will be transmitted to the cathode structure from the core or flue. As has been stated, the interior of the cathode structure is evacuated to a degree possibly slightly less than a high vacuum. For greater efliciency, the outer surface of the wall of the cathode 1 is coated with material capable of emitting electrons.

As shown, the cathode and the plate structures are provided with negative and positive terminals, so that suitable connections can be made to power lines or other current conducting circuits as may be desired.

The base walls of the cathode and plate structure will be made of thickness and strength to meet requirements, and since it is desirable that the cathode be brought to a high heat and that the plate 5 remain cool, various expedients can be resorted to to insure that the plate will not overheat.

The efiiciency of this construction may be increased by filling the interior of the cathode with some inert or other gas, and perhaps by using or supplying wires with in the cathode, wires of various material which can be readily coated with an electron emitting oxide, for example nickel or nickel alloy. Further, it is possible that the wires may have a thin coating of barium-calciumstrontium oxide to serve as an insulation and an electron emitter. While I mention that the outer surface of the Wall 1 of the cathode is coated with a material that will emit electrons, it can also be constructed of material which will emit electrons, such as thoriated tungsten. it is believed that a coating such as used in radio tubes would very likely prove best in use as it will emit electrons at a lower temperature.

The high vacuum space between the side wall of the cathode and the plate serves a dual purpose, one of which is to prevent injury to the electron emitting coating covering the cathode, and the other is to create a condition of minimum heat loss from the cathode.

In use, heat is applied to the cathode structure through the burner 8, while the plate 5 is maintained relatively cool, and as the cathode structure is heated the effect is to create current between the cathode and plate. The voltage will be increased by increasing the size of the apparatus.

Figure 3 illustrates a modified construction in which the parts are somewhat similar, but are varied and moditied to permit .the interior of the cathode to be filled with gas or vapor or other suitable medium or material. In this modified construction, the cathode 'has an outer wall 11 with a core or fiue 12, which are connected together as a vacuum sealed unit by top and bottom portions 13 and 14. A plate 15 is provided around the outer side of the cathode structure and 'is insulated therefrom by end rings 16 .and 17. It is of course essential that the space between the outer side of the cathode and the inner side of the plate be vacuum sealed, and the surface of the cathode is preferably coated with a material capable of emitting electrons into this vacuum sealed space.

A burner is .provided at 18 to conduct heat into and through the core or flue 12.

Negative and positive terminals 19 and 20 are provided for connection of suitable lines to draw the useable current as generated.

'In this adaptation, a plurality of metal discs or rings 21 are provided in the interior of the cathode structure between the core or due 12 and the outer wall 11, to assist in uniform heat transfer from the heating core. These discs or rings have openings therethrough permitting fiow of gases within the cathode.

In use and operation the modified construction will be substantially the same as set forth in connection with the embodiment first described.

As various embodiments of my invention occur, it is possible that the wire as described in the first disclosed embodiment can be coiled or otherwise arranged within the cathode structure, and it is possible that there are pulverant or granular materials which can be used to fill the space within the cathode structure.

Obviously, where gases or vapors are used in the cathode structure, either alone or with some solid material, the pressures will be properly regulated and maintained.

While I have herein shown and described only certain specific embodiments of my invention, it will be apparent to those skilled in the art that many changes and variations can be made without departing from the spirit and scope of my invention.

I claim:

1. An electron tube designed to convert heat directly into electricity comprising a cathode structure coated with material emitting electrons when heated, an enclosing plate structure, the coating on said cathode structure facing said plate structure, said cathode and enclosing plate structure being closely spaced and being insulated one from the other and having a vacuum therebetween, means to heat said cathode structure, and electrical .connections from said cathode structure and said plate structure.

2. An electron tube designed to convert heat directly into electricity comprising a hollow cathode structure closed and evacuated and containing a material generating electrons when heated, an enclosing plate structure, said cathode and enclosing plate structure being closely 4 spaced apart on their side walls and being sealed and insulated one from the other and having a high vacuum therebetween, means to heat said cathode structure, and electrical connections from said cathode structure and said plate structure.

3. An electron tube designed to convert heat directly into electric current comprising a hollow cathode structure of substantially cylindrical form having a hollow core through its center and being closed and sealed at top and bottom, said cathode structure containing a material which through transmission of heat from said core will generate electrons, a plate of generally cylindrical form surrounding the outer wall of said cathode structure and thermally and electrically insulated therefrom and having the space between the cathode and plate evacuated, means to impart heat to said cathode structure through said core, and electrical connections from said cathode structure and said plate structure.

4. An electron tube designed to convert heat directly into electric current comprising a hollow cathode structure of substantially cylindrical form having a hollow core through its center and being closed and sealed at top and bottom, said cathode structure having its outer surface coated with a material which through transmission of heat from said core will generate electrons, a plate of generally cylindrical form surrounding the outer wall of said cathode structure and thermally and electrically insulated therefrom and having the space between the cathode and plate evacuated, means to impart heat to said cathode structure through said core, electrical connections from said cathode structure and said plate structure, andperforated metallic discs in said cathode structure intermediate the core and the outer wall to aid in heat transmission.

'5. An electron tube designed to convert heat directly into electric current comprising a hollow and substantially cylindrical cathode structure of considerable size having a flue extending through the middle thereof and with the top and bottom closed, the space within said cathode being closely packed with fine gauge wire coated with refractory insulation, a shell of. only slightly larger diameter than the outside of said cathode fitted therearound and insulated electrically and thermally from said cathode, the space between the cathode and plate being relatively narrow and being evacuated, said cathode having the surface thereof facing the shell surfaced with a coating of material capable of emitting electrons when heated, positive and negative terminals on said cathode and shell, and heat supplying means at the lower end of said core or flue to heat the same and to bring the cathode structure to a high temperature while the thermally insulated .plate remains relatively cool.

References Cited in the file of this patent UNITED STATES PATENTS 2,510,397 Hansell June 6, 1950 

